BaseDaoImpl

//------------------------------------------------------
import java.util.List;
public interface BaseDao {
void save(Entity obj) throws Exception ; 
void update (Entity obj) throws Exception; 
void delete(int id) throws Exception; 
List findAll() throws Exception;
Entity findById( int id) throws Exception;
}
//----以上是BaseDao
//-----------------------------------------------------
package com.base;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.util.DBUtils;
/**
 * jdbc连接 ： 1创建连接对象  2拼sql 3 preparedstatemenet
 * @author _oiYc
 * @param <Entity>
 */
public class BaseDaoImpl<Entity> implements BaseDao<Entity>{
//public 
protected Class clazz ;
public BaseDaoImpl(){
//System.out.println(this.getClass());
ParameterizedType pt = (ParameterizedType) this.getClass().getGenericSuperclass();
//带有真实类型参数的对象
clazz = (Class)pt.getActualTypeArguments()[0];
System.out.println(clazz);
}
/**
* 保存方法
*/
public void save(Entity obj) throws Exception {
//obj.getSimpleName();
Connection conn = DBUtils.createConn();
String sql = "insert into " + clazz.getSimpleName() + " values(null ";
// 可以获取本类所声明的变量
Field[] fs = clazz.getDeclaredFields();
//System.out.println(fs.length);
for (int i = 1; i < fs.length; i++) {
sql += ",? " ;
}
sql = sql + ")";
System.out.println(sql);
//进行预编译
PreparedStatement ps = DBUtils.getPs(conn, sql);
//ps.setString(1, user.getName());
for (int i = 1; i < fs.length; i++) {
//拼接方法的名称
String MethodName = "get" +Character.toUpperCase(fs[i].getName().charAt(0)) + fs[i].getName().substring(1) ;
Method m = clazz.getMethod(MethodName);
ps.setObject(i, m.invoke(obj));
}
ps.executeUpdate();
DBUtils.close(ps);
DBUtils.close(conn);
}
/**
* 更新方法
*/
public void update(Entity obj) throws Exception {
Connection conn = DBUtils.createConn();
// update user set name = ? , age = ? where id = ?
String sql = " update " + clazz.getSimpleName() + " set  ";
Field[] fs = clazz.getDeclaredFields();
for (int i = 1; i < fs.length; i++) {
sql += fs[i].getName() + "=?,";
}
sql = sql.substring(0, sql.length()-1) + " where id = ? ";
PreparedStatement ps = DBUtils.getPs(conn, sql);
for (int i = 1; i < fs.length; i++) {
String methodName = "get" + Character.toUpperCase(fs[i].getName().charAt(0)) + fs[i].getName().substring(1);
Method m  = clazz.getMethod(methodName);
ps.setObject(i, m.invoke(obj));// user.getName();
}
Method m2 = clazz.getMethod("getId");
ps.setInt(fs.length,(Integer)m2.invoke(obj));
ps.executeUpdate();
DBUtils.close(ps);
DBUtils.close(conn);
}
/**
* 根据一个id 查找对象
*/
public Entity findById(int id) throws Exception {
Connection conn = DBUtils.createConn();
String sql = " select * from  " + clazz.getSimpleName() +  " where id = " + id ;
PreparedStatement ps = DBUtils.getPs(conn, sql);
ResultSet rs = ps.executeQuery();
Entity entity =  (Entity) clazz.newInstance();
if(rs.next()){
Field[]  fs = clazz.getDeclaredFields();
for (int i = 0; i < fs.length; i++) {
String methodName = "set" + Character.toUpperCase(fs[i].getName().charAt(0)) + fs[i].getName().substring(1);
Method m = clazz.getDeclaredMethod(methodName, fs[i].getType());
m.invoke(entity, rs.getObject(fs[i].getName()));
}
}
DBUtils.close(rs);
DBUtils.close(ps);
DBUtils.close(conn);
return entity;
}
/**
* 查询所有
*/
public List<Entity> findAll() throws Exception {
Connection conn = DBUtils.createConn();
String sql =" select * from " + clazz.getSimpleName();
PreparedStatement ps = DBUtils.getPs(conn, sql);
List<Entity> list = new ArrayList<Entity>();
ResultSet rs =  ps.executeQuery();
while(rs.next()){
Entity entity = (Entity)clazz.newInstance();
Field[] fs = clazz.getDeclaredFields();
for (int i = 0; i < fs.length; i++) {
String methodName = "set"+ Character.toUpperCase(fs[i].getName().charAt(0)) + fs[i].getName().substring(1);
Method m = clazz.getMethod(methodName, fs[i].getType());
m.invoke(entity, rs.getObject(fs[i].getName()));
}
list.add(entity);
}
DBUtils.close(rs);
DBUtils.close(ps);
DBUtils.close(conn);
return list;
}

/**
* 删除方法
*/
public void delete(int id) throws Exception {
Connection conn = DBUtils.createConn();
String sql = " delete from " + clazz.getSimpleName() + " where id =" +id;
PreparedStatement ps = DBUtils.getPs(conn, sql);
ps.executeUpdate(sql);
DBUtils.close(ps);
DBUtils.close(conn);
}
/**
* 条件查询的反射封装方法
* @param sql
* @param params
* @return
*/
public  List<Entity> queryListForParams(String sql,Object[] params ) throws Exception{
Connection conn  = DBUtils.createConn();
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
// 建立statement对象(封装了sql)
ps = conn.prepareStatement(sql); // select * from org where id = ? and name = ?  [1 , z3]
if(params!=null){
for(int i=0;i<params.length;i++){
ps.setObject(i+1, params[i]);
}
}
Field[] fs = clazz.getDeclaredFields();
rs = ps.executeQuery();
while(rs.next()){
Object obj = clazz.getConstructor().newInstance();
for(int i = 0 ; i <fs.length;i++ ){
String methodName = "set" +fs[i].getName().substring(0, 1).toUpperCase()+fs[i].getName().substring(1);
Method m = clazz.getMethod(methodName, fs[i].getType());
Object value = rs.getObject(fs[i].getName());  
m.invoke(obj, value); 
}
list.add(obj);
} 
} catch (Exception e) {
e.printStackTrace();
}finally{
DBUtils.close(rs);
DBUtils.close(ps);
DBUtils.close(conn);
}
return list;
} 
}